Production of pyrrocolines



Process Corporation, Wilmington, .Del.,- 'a' corpora l lw .7 v

' lhepi'e'sent invention relates to catalytic dehli rocyclii zation of ortho-substituted ridin' and i e'ridine com-' v py p p dilute aqu'eous solutionof a water soluble platinum salt pounds to produce fused hereteocyclic poly-ring structures containing a common carbon and nitrogen atom, as exemplified by the structure Ema, WilmingtomDeL, a s's ignor'to' -l lontlilry on T thecarrieri Alumina in the form of activated or gamma k containing gaso containing apyridine or piperidine nucleus having an alkyl oraalkenylgroup of at least' 3 carbonatorns ina straight chain or an alkaryl group attached in a position "rtho to the heteroN, are subjected in vapor phase to dehydrocyclization in the presence of supported platinum orfpaladiurn'catalyst to efiect ring closure with the forma tion of a pyrrole type structure at the commonhe'tero' n t Q n- A 9 if, hereaction is'carried out at temperatures in the range of 75 Oto 900 F. and preferably in the presence of added hydrogen, which may be in i theheterocyclic reactant. It is not necessary'io employ superatmosphe'ric pressures in carrying'outthe' process; I The reaetion'n'iechanism can be exemplified by thefolf molar ratioof 1:1 to 20:1 to

alumina" 'is the" preferred carrier; other supports include silica g'el,silica-alumina,-or magnesia.

Platinum catalyst, useful in the present invention ean be prepared by impregnatingactivated alumina-with a or complex in sufiicient amount to provide the desired quantity of metal, preferably 0.5 to -l.0% by weight'of carrier,*followed by drying and reduction with hydrogen If chloroplatinic acid-or other halogen-containing platinum (or paladium) compound is employed for impregnation of the alumina, all or part of the halogen will be retained in the catalyst'and confer an'acid function. While such alumina-supportedcatalysts containing nalo mcan be used, these tend to promote' scissi'on, polymerization and "other uridesiredside reactions, necessitating "more carefulcontrol'ofoperating conditions and'even then'may reduce the yields 'of desired products. *Forthe'se' "reasons it ispreferredto employ-catalysts having' alumina'carriers' substantially free'of halogen; such as those co'ntainingO to'less" than 0.05 %"halo'g'en'.- Such eatalys'ts'can' bepre' pared by using soluble platinum or"palladium compounds other thanthose'containing halogen, 'orb'ystearning the halide-containing impregnated alumina until the halogen has *been 'remov'edbr reduced to the stated limits. I

'Theuse'of startin'g'alkyl or alkenyl pyridine or'pipri 'dinejcompounds containing more than 6 carbon atomsin the side chain'is' 'not recommendedinasmu'ch as splitting of the chain'andthe possibility'o'fothersidereactioiis increases'with increasinglength'off h chain;

(alpha propyl pyridine) the reaction would include, under the same operating conditions, dehydrogenation of, the side Eliainto the'olefinic group, withthe resulting production of'pyrfocoline.. a

i lnsteadbf the substituted pyridines one cane'mploy fliekorresponding .alkyl or alkenyl piperidines. .Under thelde'scribe'd .operating. conditions, dehydrogenation of fliepip'eridine nucleus would take'place. It may be possible by proper close control of operating conditions to retain the piperidine nucleus in hydrogenated state; lower temperatures and higher hydrogen partial pressures favor 1;.

hydrogenation. i-Compounds of the delta coniceine type could thus be obtained.

1 e': e =t 0n f, -alkml r fll py id 1 1 illustrated by the following:

a 2-(0-toly1) pyridine 1,2-benzpyrroeoline 'Ihe pyr'rocoline compounds obtained are useful as intermediates fonthe preparation of polymethine" dyes which have been advocated for'use in light filters and as antihalation compounds in photographic I emulsionsi Known dyes-of thisclass include those formed by reaction of alkyl or aryl substituted pyrrocolines with vinyl benzf' oxazole acetanilide "and those obtained by condensing-of pyrrooolinecouipounds with trialkoxy propene,

M 1 JExampleIw V: 23 S volu'mes (as liquid) comprising 247partsby eight of 2I-benzy1" pyridine were passed as vapoiin a carrier gas through a fixed bed reactor containing 40 volumes" of steamed platinumron-alu'mina catalyst at910". F.', at at mos'pheiic pfessnrqian at asp ce rate or 0.7s'1vo1 mej reactant, per homiper' voiume'or catalys't'.-g Hydrogen was used as carrier gas for vaporizing the benzyl pyridine: to its admission to the catalytic reactor, in a mol ratiot the benzyl pyridine of4:1.-

, W fflueit'fwas passed through' a tap water amed. cbndenser with the formation or bright ,ifyenow crystals'of 2,3-benzpyrrocoline' in the condenser and the. recovery of 197 parts by weight'liquid producz" s6%' The, reaction;

; H 5 liquid recovery). On cooling the liquid Product in the receiver to 8 C-, additional C y of the pyrrocoline were produced; which together with the crystals washed from the condenser totaled 5 parts by weight.

The mother liquor, which contained in addition to noncrystallized 2,3-benzpyrrocoline unreacted 2-benzyl pyridine and traces of anthracene, was fractionally distilled to yield a recycle charge and 9 parts by weight of a solid residue of crude 2,3-benzpyrrocoline.

The bright yellow crystals of 2,3-benzpyrrocoline showed a yellow fluorescence with a greenish cast in ultraviolet light. No change in color of the crystals occurred on recrystallization from 95% ethanol, and the thus purified crystalshad a melting point of 179-l80 C. Solutions of the product in alcohol oxidized slowly in air, obtaining a non-fluorescent bright blue oxidation product. The hydrochloride of the 2,3-benzpyrrocoline was found to be soluble in water with a light pink color, and was not fluorescent. By addition of sodium hydroxide to the aqueous hydrochloride salt solution, the yellow fluorescent base was precipitated.

The loss of fluorescence on Conversion of the base to salt form can be explained on the basis of change irom the coplanar structure with consequent damping Of 10- leeular electronic resonance.

In addition to the uses named above for the py rocolines asv a class, the 2,3-benzpyrrocoline and closely related pyrrocoline compounds exhibiting similar fluorescent properties can be used in known manner as indicators for determining oxidation of packaged and other products by exposure and as components of fluorescent coloring compositions and optical bleaches.

Example II" eth Pyrid ne. d h d. with; 6 mots/ x 01 hyd ogen gas. were passed o he same c taly as use in the previous samp e. a a iqui hourly sp ce ra eof. Q15 volum per volume o cat ly t and at. F. There was obtained.

1-73. d -h.- Ahgmms 9f cm Q hqmd Pmdugt ciompnsmg' 3 e41 Y1 Of. 750. to 900 F. in the presence of at least an equal pyrreec ihe the iqu d be ng a h y fl o e cen o l h h s ve.- the usual color tests oi mo i e-compounds. The iqu d p oducts rom ever s parate runsshowved refractive ism-ice re pe iv y- (H1325). Qt 1-4 949. and

the bridge:

. indicated in the appended claims:

wherein R is: (1) an alkyl or alkenyl group of 3 to 7 carbon atoms in a straight or branched chain; or (2)'an alkaryl group containing 1 to 3 carbon atoms in the alkyl .chain and in which the aryl is otherwise unsubstituted or may be further substituted by simple non-functional groups; or (3) an aralkylgroup. containing at least one alkyl group of 1 to 3 carbon atoms in a position ortho to Obviously many modifications and yariationsof the present invention as hereinbefore' set forth lmaybe'inade without departing from'the spirit and scope thereof and therefore only such limitations should be imposdas'are I claim: a

1. The method of dehydrocyclization of o-alkyl pyridine and o-alkyl piperidine compounds to produce fused heterocyclic ring structures containing a common carbon and nitrogen atom, said compounds in non-hydrogenated .-.4 .2;. the inde o he s a n comp nd being 1.4.86.5.

7 Becau e e the m ll d fi tenc s. inbo g; p int of the. y nyrrq oline andth tarting emyl. En dte,v sepa? a ion y; hlla oh. prov d xtreme y ffi u t and nly YQYY' o yields of th et yl pytrocoline an. e thus ob tainsdt Mo e. efiec e eparation is. c mp i hed by ehtqmatosrap ic ad orp ion. on. il ca or. al mina gel. or y the use base exchan e, ins, k ng adsantage-ot th d iter ses n hasici y 0 he-alkyl pyridineand: the eerre neadtns al yl pyrrocohne ob ained there rom.-

E taly t u ed in he t teseing; e amples was p e- Pars. by a in activated l ina nhe; f rm of. 4. mm. ey j. t c .:pel. .e. swith 10% ace ic acid a room tempera! ure tor an hqur- 0 ed by insing distilled-water and th reatte imptesnatina he. pe et with; a sol tion. 0t.

0.5% platinum therein. The impregnated pellets were then subjected to an air stream and dried at about 275 F. The. dr ed pe le s ere then rea e it a y o n. gas

' a ab ut 90 F .q n hou to c er th hlo p... te. o. etallic. n at l um fello ingwhieh the cataly wa el de y rea men i h. a Qf y dtqg n nd 0% steam), at 0? igandi ag in-s j to. .00% hydr en. rea me t t he. same emperature'for a her hour. fin shed-ca alys cont n 0-17 1 by W ight, 9. g mma al mina/and 5% platinum. The en r l eact on or p od cti nofi py oh'n type cemn nnds by e ydrocyclizafiq is. ap licable to substitme ny jdines (a d. he cr esncndi hapiperidine c m Ba lad Qfithe ormula form having the formula wherein R is a substituent selected from the group consisting of: (1) alkyl and alkenyl radicals of 3 to 7 carbon atoms. (2) alkaryl radicals containing 1 to 3 carbon atoms inthe'alkyl chain and ('3) aralkyl radicals containing at least one alkyl. group of 1 to 3 carbon atoms in a'posin'on ortho. to the bridge; which method comprises passing such compounds in, vapor state. at a temperature in the range molar quantity of added hydrogen, over. supported noble metal, catalyst composed of 0.1. to 3% platinum on acti= vated alumina substantially free of halide.

2..v The method of producing heterocyclic compounds containing a pyrrocoline structure which comprises dehydrlocyclization of an ortho-substituted hydrocarbonpyridine compound containingat least 3 carbon atomsin the hydrocarbon substituent, by contact in vapor state with platinum catalyst supported on a substantially non-acidic carrier composed of alumina substantialty fi'eeof halide, at a temperature in the range of 750 F. to 900 F. min the presence of added hydrogen.

3. The method of producing 2,3-benzpyrrocoline, which comprises passing 2-benzyl pyridine over supported-platinum catalyst at a temperature in the range of 750 tot900 F. and in the presence of added free hydrogen, said catalyst consisting essentially of 0.1 to 3% platinum on activated alumina. substantially free of halide.

References Cited in the file of this patent 70B, pp.. 1767-76 1937 

1. THE METHOD OF DEHYDROCYCLIZATION OF O-ALKYL PYRIDINE AND O-ALKYL PIPERIDINE COMPOUNDS TO PRODUCE FUSED HETEROCYCLIC RING STRUCTURES CONTAINING A COMMON CARBON AND NITROGEN ATOM, SAID COMPOUNDS IN NON-HYDROGENATED FORM HAVING THE FORMULA 